1) Field of the Invention
This invention relates generally to audio processors that incorporate limiting and compression techniques and more specifically to a transmission system including an audio processor that separates the positive and negative portions of an audio information signal and then re-combines the two portions in a manner that optimizes the content of the signal. The optimized information signal is then incorporated within a carrier signal to complete the transmission system.
2) Description of the Prior Art
U.S. Pat. No. 6,205,225 discloses a device in which the input signal is multiplied by a control signal. U.S. Pat. No. 6,107,879 shows an automatic dynamic range control circuit such that, when an excessively high input signal level is fed, the first circuit means can be switched to the second circuit means without distorting the output waveform. U.S. Pat. No. 5,892,834 teaches a device that compresses the dynamic range of an output audio signal. U.S. Pat. No. 5,463,695 shows a compressor whereby a control output signal changes the gain of an amplifier circuit in response to the transient peaks in the sample distorting the output waveform.
None of the above listed patents describe a polarity-independent transmission system whereby the positive and negative portions of a generally asymmetric audio information signal are separated and then optimally combined to modulate a radio frequency carrier.
Accordingly, one object and advantage of the present invention is that an asymmetric audio information signal can be separated into positive and negative components.
Another object and advantage is that the positive and negative components of the information signal may be independently acted upon by polarity-independent variable gain stages.
Another object and advantage is that the separate signals are combined to form an amplitude limited signal that will modulate a radio frequency carrier to its maximum potential regardless of input waveform asymmetry.
Further objects and advantages of this invention will become apparent from consideration of the drawings and ensuing description.
The present invention is composed of a polarity-independent transmission system that splits a generally asymptotic incoming signal into positive and negative components; each referenced to the input signal baseline. Two separate polarity-independent variable-gain amplifiers act upon the positive and negative components of the signal. A positive peak rectifier circuit permutes the positive output component of the signal and a negative peak rectifier permutes the negative output component. Each rectifier has an associated comparator amplifier that generates an error voltage that represents the difference between the signal peak level and a maximum permitted level established by fixed references. The filtered error voltages assign separate gain factors to the positive and negative waveform excursions operated on by the two polarity-independent variable-gain amplifiers. Each amplifier independently applies the gain necessary to ensure that the peak amplitudes of the positive waveform excursions and the peak amplitudes of the negative waveforms are the same, referenced to the input signal baseline. A combining amplifier sums both the independently limited positive and negative components of the signal to form an amplitude de-limited signal that is symmetrical about the referenced baseline. This signal may be used to modulate a radio frequency carrier to its maximum potential regardless of input signal waveform asymmetry.